This invention relates to elastomeric polyurethane and/or polyurea products and more particularly to an effective process for the water emulsification of liquid urethane prepolymer having blocked isocyanate curing sites which can be activated by heating, thus enhancing the utility of these copolymers to industrial processes.
It is known that "pot life" can be increased by blocking reactive isocyanato groups in isocyanato reactive systems by adding an active hydrogen compound capable of forming an essential unreactive adduct which at elevated temperatures, e.g., higher than 70.degree. C., returns the isocyanate groups to a reactable condition. Many compounds for blocking isocyanato groups are named in the prior art including Canadian Patent No. 778,481, which discloses the use of volatile ketoximes, e.g., methyl ethyl ketoxime.
Presently, only certain organic solvent systems are used when solvents are needed for use with liquid urethane prepolymers. It would be extremely beneficial if organic solvents could be eliminated from these systems, e.g., reduce fire and health hazards, reduce cost, eliminate recycling solvent, etc.
Surprisingly, it has been found that blocked prepolymer can be emulsified in water by use of certain non-reactive or at least low reactivity emulsifiers. The emulsified product has very low viscosities in the emulsified state. This product is unique and there is no industrial precedence.